/*
   Copyright The containerd Authors.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package shim

import (
	"context"
	"fmt"
	"net"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	"github.com/containerd/containerd/namespaces"
	"github.com/pkg/errors"
)

const shimBinaryFormat = "containerd-shim-%s-%s"

// Command returns the shim command with the provided args and configuration
func Command(ctx context.Context, runtime, containerdAddress, path string, cmdArgs ...string) (*exec.Cmd, error) {
	ns, err := namespaces.NamespaceRequired(ctx)
	if err != nil {
		return nil, err
	}
	self, err := os.Executable()
	if err != nil {
		return nil, err
	}
	args := []string{
		"-namespace", ns,
		"-address", containerdAddress,
		"-publish-binary", self,
	}
	args = append(args, cmdArgs...)
	name := BinaryName(runtime)
	if _, err := exec.LookPath(name); err != nil {
		if eerr, ok := err.(*exec.Error); ok {
			if eerr.Err == exec.ErrNotFound {
				return nil, errors.Wrapf(os.ErrNotExist, "runtime %q binary not installed %q", runtime, name)
			}
		}
	}
	cmd := exec.Command(name, args...)
	cmd.Dir = path
	cmd.Env = append(os.Environ(), "GOMAXPROCS=2")
	cmd.SysProcAttr = getSysProcAttr()
	return cmd, nil
}

// BinaryName returns the shim binary name from the runtime name
func BinaryName(runtime string) string {
	parts := strings.Split(runtime, ".")
	// TODO: add validation for runtime
	return fmt.Sprintf(shimBinaryFormat, parts[len(parts)-2], parts[len(parts)-1])
}

// AbstractAddress returns an abstract socket address
func AbstractAddress(ctx context.Context, id string) (string, error) {
	ns, err := namespaces.NamespaceRequired(ctx)
	if err != nil {
		return "", err
	}
	return filepath.Join(string(filepath.Separator), "containerd-shim", ns, id, "shim.sock"), nil
}

// Connect to the provided address
func Connect(address string, d func(string, time.Duration) (net.Conn, error)) (net.Conn, error) {
	return d(address, 100*time.Second)
}

// AnonDialer returns a dialer for an abstract socket
func AnonDialer(address string, timeout time.Duration) (net.Conn, error) {
	address = strings.TrimPrefix(address, "unix://")
	return net.DialTimeout("unix", "\x00"+address, timeout)
}

// NewSocket returns a new socket
func NewSocket(address string) (*net.UnixListener, error) {
	if len(address) > 106 {
		return nil, errors.Errorf("%q: unix socket path too long (> 106)", address)
	}
	l, err := net.Listen("unix", "\x00"+address)
	if err != nil {
		return nil, errors.Wrapf(err, "failed to listen to abstract unix socket %q", address)
	}
	return l.(*net.UnixListener), nil
}

// WritePidFile writes a pid file atomically
func WritePidFile(path string, pid int) error {
	path, err := filepath.Abs(path)
	if err != nil {
		return err
	}
	tempPath := filepath.Join(filepath.Dir(path), fmt.Sprintf(".%s", filepath.Base(path)))
	f, err := os.OpenFile(tempPath, os.O_RDWR|os.O_CREATE|os.O_EXCL|os.O_SYNC, 0666)
	if err != nil {
		return err
	}
	_, err = fmt.Fprintf(f, "%d", pid)
	f.Close()
	if err != nil {
		return err
	}
	return os.Rename(tempPath, path)
}

// WriteAddress writes a address file atomically
func WriteAddress(path, address string) error {
	path, err := filepath.Abs(path)
	if err != nil {
		return err
	}
	tempPath := filepath.Join(filepath.Dir(path), fmt.Sprintf(".%s", filepath.Base(path)))
	f, err := os.OpenFile(tempPath, os.O_RDWR|os.O_CREATE|os.O_EXCL|os.O_SYNC, 0666)
	if err != nil {
		return err
	}
	_, err = f.WriteString(address)
	f.Close()
	if err != nil {
		return err
	}
	return os.Rename(tempPath, path)
}